Process of hardening concrete structures.



S. W. FLBSHEIM.

PROCESS OF HARDENING CONCRETE STRUCTURES.

APPLICATION FILED AUG.11,1918.

1, 1 1 3, 1 l2. P n ed 0ct.6,1914.

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SYLVESTER W. FLESHEIM, OF CLEVELAND, OHIO, ASS IGNOR TO THE MASTER BUILD:- ERS COMPANY, OECLEVELAND, OHIO, A CORPORATION OF OHIO.

PROCESS OF I-IARDENING CONCRETE S'JERUC'IU'RES.

To all whom it may concern Be it known that I, SYLVESTER W. FLES- HEIM, a citizen of the United'States, residing at Cleveland, in the county of Cuyahoga and State of Ohio, have invented a certain new and useful Improvement in Processes of Hardening Concrete Structures, of which the following is a full, clear, and exact description, reference being had to the accompanying drawings.

This invention relates to concrete structures, such as floors, driveways, walks, walls, ceilings, roofs, reservoirs, and the like; and particularly to such structures as are subject to heavy wear like floors, walks, and roadways, or to structures which are subject to severe climatic conditions, such as roofs and docks or to structures which are continually subject to the action of moisture, such as clams, embankments, reservoir interiors, conduits, and the like in which leakage or per.- colation of the water is undesirable by reason of disintegration, contamination or mechanical weakening.

It is a well known fact that if a concrete structure be carefully surfaced as by troweling, 01 be carefully rubbed down to a stone finish, the efiects of water and weather will be withstood for a com aratively long time and the structure will s ow little if any deterioration. However, if this surface be punctured or abraded as is almost unavoidable in driveways, walks, or floors, or in structures upon which or against which ice may form, such puncture not only operates to give access to moisture but forms a center of disintegration which rapidly spreads until a comparatively large surface has become seriously damaged even though little water be present.

It has heretofore been proposed to mix.

with the concrete mass or grout prior to the la ing or casting thereof a large percentage of metallic iron particles together with a corroding or oxidizing agent such as hydrochloric acid, alum or the like, with the intention that these iron particles should be come oxidized or rusted after the setting of the concrete with the hope that they would impart greater hardness and wearing qualities to the same and would increase its resistance to the penetration of moisture. Just why the friable and non-adherent iron Specification of Letters Patent.

Application filed August 11, 1913.

Patented Oct. 6,1914.

Serial No. 784,073.

a floor by reason of-the breaking up of the surface layers, has been given an unpleasant color, and has stained all fabrics and the like which came in contact therewith.

The object of the present invention is the provision of a process for imparting the requisite hardness, impenetrabllity andwearing qualities to a structure of this nature, with the employment of a minimum amount of material; the provision of a method for hardening or indurating the surface layers of such a structure which shall bear the same relation to the previously known means for hardening the same as the case hardening of iron bears to the manufacture of steel; the provision with the use of a very small quantity of pulverized metal, of a concrete structure which shallbe absolutely dustless and free from any tendency to scaling, abrasion, or disintegration, the provision of a method whereby all of the material can be employed without waste; the provision of a concrete structure whose surface shall be smooth, lastin and attractive, and in which the danger o staining objects which come in contact therewith shall be obviated; while further objects and advantages of my invention will become apparent in the course of the following description and claims.

The invention consists essentially in ap} plying to the surface of a concrete structure immediately after the same has been laid or poured, and before it has had an opportu nity to dry, harden, or set, a comparatively thin layer'of pure, fresh, slightly alkaline cement mixed with a large proportion of finely divided metallic iron in the form of irregular jagged particles and thoroughly floating the same upon and into the surface of the concrete. Thismaterial is referably applied in the dry state, being si ted evenly into lace in the case of a horizontal surface and eing thrown or dusted into place in the case of a vertical surface. The floating serves to induce the penetration of moisture into this dust coat from the wet concrete therebeneath, and to rub the iron particles about in the cement with which they are applied s as to cause them to become coated all over with the pasty cement-and-water mixture. It also causes this surface coating to adhere firmly to and actually to become incorporated somewhat with the underlying concrete,- although care is taken not to continue the floating so long as to cause any of the sand grains to penetrate through the dust coat. As soon as this surfacing layer has become thoroughly moistened by the floating and the metallic grains havedoecome thoroughly coated with the cement-paste, it is carefully smoothed and pressed down by burnishing with a steel trowel so as to render the surface hard and dense and to press the iron particles into close juxtaposition with. each other. The irregular and jagged charact'erl'of the iron particles also causes them" to interlock in large measure thus forming a surface coating over the original concrete which is almost entirely of iron.

During the operation of floating, the iron particles which are of very much greater size than the cement particles, become entirely surrounded with the fine cement flour,

and also thoroughly moistened with the wa- I ter derived from the original concrete. As the iron grains are pressed together by the troweling, the cement particles serve to fill up the spaces between them in the same manner as pitch is employed to fill the spaces between paving blocks, and these cement particles immediately begin to combine with the water forming the adhesive double silicate of aluminum and calcium whichgis the fundamental constituent of concrete and thus to bind the iron grains closely together, this binding being much facilitated by the irregular character of the metallic grains. As soon as this hydration of the cement particles has thoroughly begun but prior. to the completion of the same and while the surface layers are still somewhat'plastic, the surface is thoroughly and carefully troweledia second time for the purpose of burnishing' the iron grains and compacting them still more closely. This second troweling is much more thorough thanthe first trowelm' and a much higher pressure is .employedlin fact, as much as the workman can exert. It would be entirelyimpossible to. impart this force upon the first troweli ng owing to the soft and squashy condition of the concrete at that time. The result of thissecond troweling is the compacting of the surface portions into a very solid impervious mass. .After this second troweling the surface is kept moist for at least three or four daysso as to permit the com plete hydration of the cement particles. In the case of a floor or other horizontal surface this may be effected by covering the same completely with water or by covering with wet sawdust or hay, and in the case of walls by spraying with water from time to time. I

This process produces a surfaceihaving a smooth glossyappearance which Will be entirely impervious to fluids, will be wearroof, dust-proof,- and also almost indestructlble. The object of the cement is to bind the iron particles in place and to form a matrix for'holding them together and for filling theinterstices therebetween. The metallic iron grains by reason of their tenacity, malleability and ductilityare extremely resistant to abrasion or disintegration. The

alkaline character of the cement. absolutely prevents any oxidation of the iron grains even though the structure be submerged inwater for extended periods or be alternately sub ected to water and air. Oxidation is also prevented-by the'fact that each grain is surrounded completely by a thin shell of silicate crystals whereby the access of oxygen thereto is prevented.

In the drawings accompanying and forming a part of this specification I have illustrated the character of a structure produced by the process herein described.

In these drawings, Figure 1 is a transverse cross-sectional View through a portion of the concrete structure having its surface treated in accordance with my invention and Fig. 2 is'a plan view of a portion of the surface so/treated, the same being magnified from eight to"ten times.

In these drawings the metallic grains are indicated at AA, and the concrete inatrix in which they are embedded at .BB. The original concrete structure upon which this surface is laid is illustrated at C, and the locality in which one layer merges with the other layer is indicated generally at D. The richnessof the various portions in iron grains is indicated by the density of the black dots in Fig. 2- of the drawings. .The line of demarcation between these layers is usually somewhat wav and irregular due to the intermixing of t e layers at their boundaries occasioned by the floating operation.

It is essential to the successful performance of -my process that the metal grains be I these are undesirable because 0 their greater tendency to oxidize'and larger particles are undesirable becauseofthe difficulty of pressing them closely together so as to form an 1 unbroken surface. An admixture of a small idizin a ents like sal-ammoniac alum 0xalic acid and the like, are to be carefully avoided. The avoidance of rusting is also largely due to the care employed in troweling, since a well-troweled piece of work will almost never show signs of oxidation. This is apparently due to the more intimate character of the contact between the cement and the iron particles.

The original concrete can, if desired, be mixed with a certain proportion of finely divided iron particles, and such admixture is sometimes advantageous as furnishing small sized filling grains of-a more jagged and irregular character than sand of equal fineness. The use or non-use of these iron grains in the body of the concrete is entirely foreign to the present invention.

In practice I prefer to employ for the surfacing layer a mixture of cement and finely divided iron in substantially equal parts by weight, although these proportions can be varied widely without departing from the scope of my invention. These ingredients may be mixed in the dry state and stored in cans provided only that they be kept dry since the moistening of the concrete would cause it to become hydrated in part and to gather into lumps. The use of the material by sprinkling or dusting in the dry state avoids all loss by reason of making up of too much mixture at a time and also insures the employment of substantially the correct amount of moisture. This mode of use also prevents the segregation of the elements of the mixture by reason of their difference in size and gravity.

By the word cement as used in this application I mean any good, finely. ground, hydraulic or Portland cement, fresh and free from lumps, containing a small proportion of free lime, and not air slaked. By f concrete I mean a mixture of cement and a suitable aggregate such as sand or graded gravel, 'wetted up with water-and applied in the usual manner. By floating I refer to the rubbing of the surface with a wooden trowel or float in the manner well understood by masons and stucco workers who desire to obtain a dull or matte finish. By troweling I mean rubbing or burnishing with the flat face of a smoothsteel trowel.

I have mentioned iron throughout this specification as the metal which I use and this is to the best of my present knowledge the only material which can be employed upon a commercial scale with satisfactory results. Sand grains of equal size are very smooth sided and have a glassy or vitreous whereas cast iron particles have an irregular,

fracture to which the cement crystals adhere only weakly. Even the so-called f sharp sand has acute angles only at edges and corners which are comparatively infrequent 0 hackly, fracture to which the cement adheres 7 with great tenacity and which causes them to become closely interlocked by the pressure due to the troweling. Brass filings,- While quite irregular, are very expensive and the electro-negative character of the zinc I therein causes them to corrode rapidly in the alkaline medium, while the electro-positive character of the iron causes it to withstand corrosion. Copper, gold,.silver and nickle while strongly electro-positive and so free from any tendency to oxidize, are prohibitively expensive and difficult to obtain in the form of jagged and irregular particles. Minerals which have a hackly fracture, like feldspar, are too brittle and subject to wear, Wherefore iron is the only material I lmow of which will fulfil the requirements of cheapness and operativeness.

Having thus described my invention, what I claim is 1. The process of hardening a concrete structure so as to prolong the life thereof which consists in applying to 'the surface of such structure prior tq its setting a dry mixture of cement and irregular shaped grains of metallic iron, thoroughly rubbing the same into contact with thesurface of said structure so as to moisten the same, and

ally troweling the same to a smooth burnished surface.

2. The process of case-hardening the surface of a concrete structure which consists in (first) applying to the surface of said structure prior to its setting a layer of cement containing fine, irregular shaped grains of iron, (second) thoroughly rubbing the same into contact with said "first structure, (third) troweling said surface to a smooth, burnished, metallic finish and (fourth) maintaining such surface in a moist condition until said concrete has become thoroughly hydrated and "set.

3. The prosess of case-hardening the surface of a concrete structure which consists in applying to the surface of said structure prior to its hardening a layer of dry cement containing finely comminuted metallic iron particles and afterward rubbing and trowel-' ing the same into contact with said first structure. until the said layer has become thoroughly wetted by the moisture from the concrete and the iron particles have become intimately interlocked and incased with cement-paste. a"

4:. The process of hardening and rendering impervious, wear-proof, and impenetrable the surface of a concrete structure which consists in applying to the surface of said structure, prior to its setting, a dry layer of 130 cement and. finely divided metallic ironwpar ticles in substantially equal proportions 'by weight and thoroughly troweling said last In testimony whereof, I hereunto afiix my signature in thepresence of two witnesses.

SYLVE STER W. FLESHEIM.

Witnesses:

HAROLD E. SMITH, HUGH B. MCGILL. 

